Last week at TechCrunch Disrupt, Google VP of Location and Local Services Marissa Mayer took the stage for an interview with our own Michael Arrington, where they discussed everything from Google’s mobile growth to Mayer’s investment strategy. A few minutes after the interview, I had the chance to ask her a few more questions about Google’s approach to mobile and local. It’s only been a few weeks since I interviewed Mayer about Google’s two pillar approach to local, but I still had plenty of questions.

The first thing I asked: what happens if and when Apple decides to swap out the Google Maps application that ships with every iPhone, iPod Touch, and iPad in favor of something that it built in-house (Apple has confirmed that it’s working on an improved traffic database, and has also quietly acquired some mapping-related startups).

Unsurprisingly, Mayer mostly skirted the question — instead she pointed out how huge Google Maps’s audience is, with some 200 million active users on its Mobile products alone. She also mentioned some of the innovations that Google has made recently with Maps, including the new vector-based tiles that require 1/100th the data (the iOS version of Maps doesn’t take advantage of this feature).

Next, I asked if there were any technologies coming up that would help phones more accurately determine your location. Because while the Wifi/GPS combo works pretty well in most places, reliability takes a nose-dive whenever you’re in a dense city like NYC.

Mayer says that the Wifi hotspot database that Google has been building out will help with this, because it will improve over time. This is one reason why Google is going to be pushing users to explicitly check-in using Latitude — in addition to providing a new channel to engage with consumers, these check-ins also help Google improve its database. The system may not know your exact GPS coordinates, but if if someone with the similar signals previously checked in at In-N-Out Burger, there’s a good chance that’s where you are. Mayer likens the system to the powerful spell checker that often pops up in Google search.

Finally, I asked about serendipitous suggestions on mobile phones, which Mayer has previously said she’s excited about. Mayer says that she thinks we’ll see these “inside of a two year horizon”. The UI for what these suggestions will look like is still TBD, but it sounds like initially they’re be pronounced rather than subtle.